I usually throw everything in one go, up to yourself if you want to brown the sausages off first.
However last time I tried this they did end up slightly overcooked.
Cook for 4 hours on high and remainder on a low heat keep checking to see when done to your desire
Sauce goes in last to cover all the ingredients and keep stirring occasionally, however I have on occasion left this cooking all day on low if I'm out and about.